Optimizing JavaScript for Download Speed

A lightweight interpreted language, JavaScript is ideally suited to data validation, interactive forms, and enhancing navigation. Presented with such a broad toolset to play with, many authors have gone overboard with JavaScript, bulking up their sites at an alarming rate. Fortunately, JavaScript offers rich opportunities for file size and execution speed optimization. By using techniques like packing, compression, and obfuscation, you can realize 50 to 90 percent savings off the size of your JavaScript files. This chapter shows you how to put your JavaScripts on a low-char diet. In Chapter 10, "Optimizing JavaScript for Execution Speed," you will learn how to speed up the execution speed of your code.
Here's an excerpt from WebReference.com.

Crunching and Obfuscation

This free Windows program is an ECMAScript pre-processor written in JScript. In addition to removing whitespace and comments from JavaScript, it can optionally rename variables in JavaScript. For IE5.5+ Win. From Saltstorm.

Semantic Designs offers industrial strength source code obfuscation and optimization tools for JavaScript and other languages. The ECMAScript formatter can either format JavaScript applications into readable form, or it can conversely protect the source code against reverse engineering by removing structure, comments, and scrambling identifier names. For Windows.